The present invention is in the field of computer performance monitoring equipment.
Computer performance monitoring has become an established industry within the much larger data processing industry. Performance monitoring is necessitated by the high costs of equipment, the large variety of hardware and software, and the need to optimize the utilization of such equipment. Broadly, monitoring equipment provides the user with information concerning the events taking place in computer equipment, when such events take place, and the frequency of such events. Both hardware and software and combination hardware/software monitors are presently in use. The hardware picks off signals from CPUs or peripheral devices, notes the time of occurrence of such signals, stores the signals and/or the time and/or the fact of the signal occurrence, and may provide a visual output of such information to the user. Software is used principally to format the collected data in useful form for the computer user.
The standard monitors select the signals for monitoring by attaching a probe to a line inside the CPU or peripheral device carrying the signals to be measured. The probes consist of differential amplifiers which present a high impedance to the line to which they are attached. Two significant problems with this standard method are lack of flexibility and a substantial increase in probes necessary for collecting a large variety of information. For example, once the probes are attached, the signals measured are determined. To measure different signals, the probes have to be removed and attached to other lines. Also, if it is desired to measure activity in a CPU and in a plurality of peripheral devices and collect such information, a substantial number of probes would be required and it would be necessary to provide long wires from those probes attached to distant peripheral units.
Prior art monitors are the subject of several patents. Taylor, U.S. Pat. No. 3,399,298, provides direct connection to specific elements of the host computer to be monitored. The monitor counts standard clock pulses to provide an indication of a time period during which the specific element is being checked. During that time period, a second counter is provided with the same clock pulses but only during the moments while the element being monitored is active. Thus, the ratio of the two counts in the two counters indicates an efficiency measurement for the particular device being monitored.
A patent of Martin, U.S. Pat. No. 3,906,454, is directed toward a monitor for a host computer. According to the Martin patent, the host computer must be specially programmed or arranged to provide signals that indicate to the monitor that certain other signals should be accummulated or otherwise processed for monitoring.
The Deese U.S. Pat. No. 3,818,458 departs from the technique of counting or timing individual signals received from various points in a computer, but does so by only monitoring certain specific computer status indications and recording the time at which there is a change in one of these status indications.
Other standard monitoring systems or apparatus are taught by Freeman, et al., U.S. Pat. No. 3,763,474, Murphy, U.S. Pat. No. 3,540,003, Murphy, U.S. Pat. No. 3,522,597, Rash, et al., U.S. Pat. No. 3,588,837, and Kandiew, U.S. Pat. No. 3,692,989.